Diagnostics and enhanced functionality for single-wire safety communication

Abstract

A single-wire safety system architecture is provided that yields reliable safety device monitoring without the need for dual redundant signal channels. The safety system comprises a safety relay acting as a communications master device and one or more compatible safety input devices connected in series with the safety relay via a single-wire communication circuit. The safety input device farthest from the safety relay on the safety circuit modulates a safety signal with a recognizable pulse pattern that traverses the single-wire safety circuit to the safety relay via the intermediate safety devices. The safety relay maintains safety mode as long as the pulse pattern is received and recognized. In addition to conveying the safety signal, the architecture allows bi-directional communication of initialization, configuration, and diagnostic messages over the single-wire safety channel. The architecture also facilitates rapid initialization of the safety channel using asynchronous sub-link detection and device enumeration.

What is claimed is: 
     
       1. A safety input device, comprising:
 a memory that stores executable components; 
 a processor, operatively coupled to the memory, that executes the executable components, the executable components comprising:
 a safe state detection component configured to determine whether the safety input device is in a safe state; 
 a pulse detection component configured to verify that a modulated pulse pattern of a safety signal received on an input terminal of the safety input device corresponds to a defined pulse pattern; 
 a safety signal relaying component configured to output the safety signal on an output terminal of the safety input device in response to verification that the modulated pulse pattern corresponds to the defined pulse pattern and a determination that a safety function of the safety input device is valid; and 
 a message processing component configured to process an input message received via the output terminal, the input message comprising a request for device information, wherein the message processing component is further configured to, 
 in response to determining that a target address contained in the input message matches an address of the safety input device, send an output message via the output terminal, wherein the output message contains device information retrieved from the memory, and 
 in response to determining that the target address contained in the input message does not match the address of the safety input device, output the input message via the input terminal. 
 
 
     
     
       2. The safety input device of  claim 1 , wherein the safety input device is at least one of an emergency stop pushbutton, a light curtain device, a safety door switch, a safety mat device, an emergency pull-cord device, a laser scanner, or a photoelectric sensor. 
     
     
       3. The safety input device of  claim 1 , wherein the executable components further comprise:
 a pulse generating component configured to generate the modulated pulse pattern in response to a determination that the safety input device is configured to operate in a safety master mode; and 
 a safety master mode component configured to enable the safety master mode in response to detection of a terminator connected to the input terminal and to disable the safety master mode in response to determining that the terminator is not connected to the input terminal. 
 
     
     
       4. The safety input device of  claim 1 , wherein
 the input message is a first input message and the output message is a first output message, and 
 the message processing component is further configured to, in response to receiving a second input message via the output terminal indicating that a downstream safety device is active, send a second output message via the output terminal indicating that the safety input device is active. 
 
     
     
       5. The safety input device of  claim 1 , wherein
 the input message is a first input message and the output message is a first output message, and 
 the executable components further comprises a single-wire communication component configured to, in response to receipt of a second input message via the input terminal indicating that an upstream safety device connected to the input terminal is active, establish a safety channel sub-link between the safety input device and the upstream safety input device. 
 
     
     
       6. The safety input device of  claim 3 , wherein the executable components further comprise a device addressing component configured to, in response to receipt of an enumeration message via the output terminal containing an address of a downstream safety device, increment the address to yield an incremented address and assign the address to the safety input device. 
     
     
       7. The safety input device of  claim 6 , wherein the message processing component is further configured to send an enumeration response message via the output terminal, the enumeration response message containing at least the incremented address, an indication of whether the safety input device is a last addressable device on a safety circuit, and an indication of whether the safety input device is operating in the safety master mode. 
     
     
       8. The safety input device of  claim 6 , wherein the message processing component is further configured to send another enumeration message, via the input terminal, containing the incremented address. 
     
     
       9. The safety input device of  claim 8 , wherein
 the message processing component is further configured to, in response to receipt of a response message received via the input terminal as a response to the other enumeration message, output the response message via the output terminal, and 
 the response message contains at least an address of an upstream safety input device, an indication of whether the upstream safety input device is operating in the safety master mode, and an indication of whether the upstream safety input device is the last addressable device on a safety circuit. 
 
     
     
       10. The safety input device of  claim 1 , wherein the device information comprises at least one of a type of the safety input device, a product code of the safety input device, a vendor of the safety input device, a hardware revision number of the safety input device, a software revision number of the safety input device, an indication of whether the safety function of the safety input device is valid, or a device signature associated with the safety input device. 
     
     
       11. The safety input device of  claim 1 , wherein the message processing component is further configured to
 in response to determining that a target address contained in a device information request message received via the output terminal is a special address indicating a broadcast message, send a response message containing device information retrieved from the memory via the output terminal and send a relayed version of the device information request message via the input terminal, and 
 in response to determining that the target address contained in the device information request message matches an address of the safety input device, output the device information request message via the input terminal. 
 
     
     
       12. A method, comprising:
 determining, by a safety input device comprising a processor, whether the safety input device detects a safe status; 
 comparing, by the safety input device, a pulse pattern carried by a safety signal received on an input terminal of the safety input device with a defined pulse pattern; 
 in response to determining that the pulse pattern matches the defined pulse pattern based on the comparing and that the safety input device detects the safe status, outputting the safety signal via an output terminal of the safety input device; 
 processing an input message received via the output terminal, the input message comprising a request for device information, wherein the processing comprises:
 in response to determining that a target address contained in the input message matches an address of the safety input device, sending, by the safety input device, an output message via the output terminal, wherein the output message contains device information retrieved from a memory of the safety input device; and 
 in response to determining that the target address contained in the input message does not match the address of the safety input device, output the input message via the input terminal. 
 
 
     
     
       13. The method of  claim 12 , wherein the input message is a first input message and the output message is a first output message, and the method further comprises:
 in response to receiving, via the output terminal, a second input message indicating that a downstream safety device connected to the output terminal is active, configuring a second output message to indicate that the safety input device is active and sending the second output message via the output terminal. 
 
     
     
       14. The method of  claim 12 , further comprising:
 in response to receiving, by the safety input device via the output terminal, an enumeration message comprising an address of a downstream safety device, 
 incrementing, by the safety input device, the address to obtain an incremented Address, and 
 configuring, by the safety input device, the safety input device with the incremented address. 
 
     
     
       15. The method of  claim 14 , wherein the output message is a first output message, and the method further comprises:
 generating, by the safety input device, a second output message that includes at least the incremented address, a first indication of whether the safety input device is a last addressable device on a safety circuit, and a second indication of whether the safety input device is operating as a safety master device that generates the safety signal; and 
 sending, by the safety input device, the second output message via the output terminal. 
 
     
     
       16. The method of  claim 14 , wherein the enumeration message is a first enumeration message, and the method further comprises:
 generating, by the safety input device, a second enumeration message directed to an upstream safety input device, wherein the second enumeration message contains at least the incremented address; and 
 sending, by the safety input device, the second enumeration message via the input terminal. 
 
     
     
       17. The method of  claim 16 , further comprising, in response to determining that a message received via the input terminal is a response to the second enumeration message, outputting the message via the output terminal, wherein the message comprises at least an address of the upstream safety input device, an indication of whether the upstream safety input device is operating as a safety master device that generates the safety signal, and an indication of whether the upstream safety input device is the last addressable device on a safety circuit. 
     
     
       18. A non-transitory computer-readable medium having stored thereon instructions that, in response to execution, cause a safety input device comprising a processor to perform operations, the operations comprising:
 confirming that a safety signal received on an input terminal of the safety input device carries a pulse pattern corresponding to a defined pulse pattern; 
 in response to the confirming and a determination that a safety function of the safety input device is valid, outputting the safety signal via an output terminal of the safety input device; 
 receiving an input message via the output terminal, the input message comprising a request for device information; 
 in response to determining that a target address contained in the input message corresponds to an address of the safety input device, sending an output message via the output terminal, wherein the output message comprises device information retrieved from a memory of the safety input device; and 
 in response to determining that the target address contained in the input message does not correspond to the address of the safety input device, output the input message via the input terminal. 
 
     
     
       19. The non-transitory computer-readable medium of  claim 18 , wherein the operations further comprise, in response to detecting presence of a terminator connected to the input terminal, configuring the safety input device to operate as a safety master device that generates the pulse pattern and outputs the safety signal on the output terminal. 
     
     
       20. The non-transitory computer-readable medium of  claim 18 , wherein the operations further comprise:
 in response to receiving, via the output terminal, an enumeration message comprising an address of a downstream safety device, 
 incrementing the address to obtain an incremented address, and 
 assigning the incremented address to the safety input device. 
 
     
     
       21. A safety input device, comprising:
 a memory that stores executable components; 
 a processor, operatively coupled to the memory, that executes the executable components, the executable components comprising:
 a safe state detection component configured to determine whether the safety input device is in a safe state; 
 a pulse detection component configured to verify that a modulated pulse pattern of a safety signal received on an input terminal of the safety input device corresponds to a defined pulse pattern; 
 a safety signal relaying component configured to output the safety signal on an output terminal of the safety input device in response to verification that the modulated pulse pattern corresponds to the defined pulse pattern and a determination that a safety function of the safety input device is valid; 
 a device addressing component configured to, in response to receipt, via the output terminal, of an enumeration message containing an address of a downstream safety device, increment the address to yield an incremented address and assign the address to the safety input device; and 
 a message processing component configured to send an output message via the input terminal, the first output message containing the incremented address. 
 
 
     
     
       22. The safety input device of  claim 21  wherein the message processing component is further configured to, in response to receipt of an input message received via the input terminal as a response to the output message, output the input message via the output terminal, wherein the input message contains at least an address of an upstream safety input device, an indication of whether the upstream safety input device is operating as a safety master device that generates the pulse pattern, and an indication of whether the upstream safety device is a last addressable device on a safety circuit. 
     
     
       23. A safety input device, comprising:
 a memory that stores computer-executable components; 
 a processor, operatively coupled to the memory, that executes the computer-executable components, the computer-executable components comprising:
 a safe state detection component configured to determine whether the safety input device is in a safe state; 
 a pulse detection component configured to verify that a modulated pulse pattern of a safety signal received on an input terminal of the safety input device corresponds to a defined pulse pattern; 
 a safety signal relaying component configured to output the safety signal on an output terminal of the safety input device in response to verification that the modulated pulse pattern corresponds to the defined pulse pattern and a determination that a safety function of the safety input device is valid; 
 a message processing component configured to process a first input message received via the input terminal, to process a second input message received via the output terminal, to send a first output message via the input terminal, and to send a second output message via the output terminal; 
 a pulse generating component configured to generate the modulated pulse pattern; and 
 a safety master mode component configured to enable the pulse generating component in response to detection of a terminator connected to the input terminal and to disable the pulse generating component in response to determining that the terminator is not connected to the input terminal.